Apparatus for monitoring inventories of consumer goods and other products are known. The broad variety of such apparatus and their myriad modes of operation reflect not only the configurational and dimensional peculiarities of the objects whose inventory or supply is to be monitored but also the purpose for the monitoring, e.g., product identification and tracking, accounting, etc., as well as the manner in which inventory is to be taken, i.e., continuously, periodically, automatically or selectively.
In this regard, U.S. Pat. No. 3,197,620 describes a system for counting moving objects of different dimensions whereby the objects to be counted contact and displace a pivotable rod which is connected to a counting station. The counting station registers the presence of a moving object when the rod is caused to pivot in the proper direction. As a result, only cumulative tallies of objects moving in the appropriate direction are ascertainable. Such a system may be useful in environments where "one-way" counting is all that is desired or necessary. However, in situations where objects to be counted move in opposite directions past a counting station, i.e., when objects are both added and subtracted from a supply, such a one-way counting system would be of no practical use.
U.S. Pat. No. 4,797,819 teaches an inventory monitoring system for counting the quantity of articles suspended from a peg on a sales display. The system comprises an ultrasonic energy emitting and receiving gun which engages with the free end of a peg upon which merchandise is suspended. The distance between the free end of the peg and the nearest article is representative of the number of articles suspended on the peg. A microcomputer within the gun calculates this distance as a function of the time that is required for ultrasonic energy emitted from the gun to reflect from the nearest article and return to the gun. Although sophisticated, this system is readily susceptible to human error. For example, when the operator fails to properly engage the peg, neglects to appropriately orient the articles before counting, or misdirects the gun, accuracy may be detrimentally affected. Moreover, it can only be used for periodic inventory determinations and cannot provide a continuous real-time count of the articles whose inventory is to be monitored.
Systems for counting garment hangers are disclosed in U.S. Pat. Nos. 4,151,402 and 4,831,638. According to each of these references, a count of the number of garment hangers suspended from a rod is determined by moving the hangers past a stationary photosensor or moving the photosensor past a stationary rod from which the hangers depend. Neither of these arrangements can provide a real-time count of the hangers. Each system merely enables one to periodically obtain a total by moving the hangers past the photosensor or vice versa. However, between scannings, one would not know the quantity of hangers that have been added to or removed from the rod.
U.S. Pat. Nos. 4,419,734 and 4,866,255 propose inventory control systems capable of providing inventory monitoring through determination of the weights of article-supporting platforms (U.S. Pat. No. 4,419,734) and article-receiving containers (U.S. Pat. No. 4,866,255). These systems each involve article-bearing structures in operative contact with strain gauges which are, in turn, connected to computers that must perform sophisticated calculations to ascertain the number of articles borne by the article-bearing structures. The complex nature of such systems render them somewhat cost-ineffective for small-scale inventory monitoring in commercial and noncommercial applications.
A key identification and location system is provided in U.S. Pat. No. 4,673,915. The system includes a plurality of key holders, each of which releasably retains a single key that may be accessed by an authorized user. While capable of indicating the presence or absence of a key, the system has no means for counting, either in real-time or periodically, items whose inventory must be monitored.
A need exists, therefore, for an apparatus of uncomplicated design and construction for providing real-time counting of objects added to or subtracted from a location whose inventory is to be monitored.